We have investigated the performance limitations of gain-guided vertical cavity surface emitting lasers (VCSEL) which use epitaxially grown semiconductor distributed Bragg reflectors (DBR). the light-current (L-I) characteristics and emission wavelength of such lasers are examined as a function of temperature and time under continuous wave (CW) and pulsed operation. We observed a sharp roll-over in the CW L-I characteristics which limits the maximum output power. the threshold current under CW operation is found to be lower than that obtained under pulsed conditions. Several microseconds long delay in lasing turn-on is also observed. We have performed calculations, using the measured Fabry-Perot mode wavelength as a thermometer of the VCSEL active region temperature, to explain quantitatively that these anomalies are a consequence of severe heating effects. Excessive heating in the VCSEL’s results from the high series resistance of the hetero-structure DBR mirrors and the high operating current density. the heating causes a rapid shift of the gain peak relative to the Fabry-Perot mode, a reduction in gain constant at higher currents, and a thermal lensing effect. Thus, reduction of the series resistance and threshold current density can lead to significant improvements in the power performance of VCSEL's.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Electrical and Electronic Engineering